The present invention relates to a guiding and sealing unit for a mono-tube shock absorber rod and to an annular sealing assembly incorporated within.
Hydraulic shock absorbers of the mono-tube type, extensively used in the automotive and other industries, are intended to work under relatively high hydraulic pressures, in average about 20 bars, with peaks which may reach 100 bars. In view of such high working pressures, the sealing of the pressurized oil contained in the shock absorber, acts against the reciprocating motion of the piston body.
The sealing assembly of the prior art comprises many elements to be assembled separately and this is relatively cumbersome and complex to mount, and has a performance which tends to decay as the temperature decreases. In particular, when the rubber ring of DE8201327U, which constitutes the main sealing element, is formed from a particular synthetic fluorinated elastomeric material, known as FKM, the minimum working temperature of the sealing assembly is no lower than minus 15° C. degrees centigrade, when instead the current applications would require a minimum working temperature of minus 40° C. degrees centigrade.
Sealing assemblies for shock absorber rods and guiding units thereof are particularly suited to withstand fatigue stress and thus to remain efficient for a relatively long period of time are known from European patent EP1074760B1 and European patent application EP-A-06425875. However, the sealing assembly described in European patent EP1074760B1 is not adapted to be used on mono-tube shock absorbers and, like the sealing assembly according to European patent EP-A-06425875, has a smaller axial bulk size than that of DE8201327U, but still relatively high in the perspective of aiming to reduce the overall dimensions and weight of the shock absorber maintaining the same working stroke. Furthermore, the performance over time of the sliding lips of the elastomeric part of the sealing assembly can still be improved as will be disclosed.
It is the object of the present invention to provide a guiding and sealing unit for a rod of a mono-tube shock absorber and a sealing assembly therein which are free from the drawbacks of the prior art, and in particular which are adapted for application on shock absorbers of the mono-tube type, which easily withstand very low working temperatures and, more generally, working temperatures within a wide temperature range, e.g. comprised between −40° C. and +200° C., which have small dimensions, in particular in axial sense, i.e. in the direction of reciprocating motion of the shock absorber rod, which are simple and cost-effective to make and to mount, and which integrate multiple functions.